I assume this is happening in Internet Explorer.
Do the following .
Alt t - Tools
o - Internet Options
Control+tab to Programs
tab to Manage Add-ons
Tab to Filter combo box
Move up to all Add-ons and hit enter to select
Tab to the list of add-ons
The Adobe entry should look like this.
Name Adobe PDF Reader
Publisher Adobe Inc.
Status Disabled
Architecture 32-bit and 64-bit
If it is not disabled you need to make this change.
Open parent document is caused by IE trying to open the document in the
browser. By disabling this add-on it should cause Adobe reader to be opened
externally so you can read the document.
--hth---